1. Field of the Invention
The present invention generally relates to methods for preventing or treating gastrointestinal (GI) disorders. In one aspect, the invention provides methods for treating the disorders by modulating nitric oxide (NO) signaling pathways particularly in GI neurons. Methods of the invention typically involve administering at least one compound that modulates the pathway by increasing one or more of NO activity or levels of neuronal nitric oxide synthase (nNOS). The invention has a wide spectrum of useful applications including treating a variety of gastropathies by administering a therapeutic amount of at least one ofinsulin or a phosphodiesterase (PDE) inhibitor such as sildenafil (Viagra(trademark)).
2. Background
Hypomotility is one feature of a wide spectrum of gastrointestinal (GI) disorders. For example, gastric hypomotility accompanied by delayed emptying has been described. Stasis impacting the intestine, for example, is also known. See generally McCallum, R. W.(1989) in Gastrointestinal Disease, 4th ed. (Sleisenger, M. H. and Fordtran, J. S. eds.) W. B. Saunders Co., Philadelphia; and references cited therein.
Symptoms of most GI disorders generally include nausea, vomiting, heartburn, post-prandial discomfort and indigestion. In some instances, acid reflux within the GI tract can cause ulceration leading to internal bleeding and infection. The pain associated with many of the GI disorders can lead to costly and potentially life-threatening misdiagnoses of asthma or myocardial infarction. See Brunton, L. L. in The Pharmacological Basis of Therapeutics, 8th ed. (Gilman, A. G et al. eds) McGraw-Hill, Inc. New York.
Particular diseases are associated with hypomotility or stasis in the GI tract. For example, diabetic neuropathy, anorexia nervosa, and achlorhydria are frequently accompanied by gastric hypomotility. Damage to the GI tract following surgical intervention, for instance, can result in substantial gastric stasis.
Current treatment of gastric hypomotility generally involves administration of a prokinetic agent, typically domperidone, cisapride, or metoclopramide. It has been reported however that such drugs do not always impact gastric stasis and may be associated with side-effects. See Brunton, L. L., supra.
Diabetes is a common disorder worldwide resulting in significant complications including GI dysfunction. gastrointestinal dysfunction. See Porse, D. and Halter, J. B. (1999) in Diabetic Neuropathy (Dyck, P. J. and Thomas, P. K, eds) W. B Saunders Co. Philadelphia, Pa.; and Poster, D. W. (1998) in Harrison""s Principles of Internal Medicine (A. S. Fauci et al. eds) McGraw-Hill New York.
There have been attempts to study human diabetes by employing animal models. Such models include streptozotocin-induced (STZ-induced) diabetes and rodent mutants such as NOD (non-obese diabetic) mice.
There has been recognition that diabetic gastropathies involve perturbation in the normal relaxation of the pyloric sphincter; an organ that helps coordinate gastric emptying.
The NOS enzyme has attracted much attention. Under appropriate conditions, the enzyme produces nitric oxide (NO). See e.g., U.S. Pat. Nos. 5,439,938; 6,103,872; and 6,168,926 to S. H. Snyder et al. for general disclosure relating to NOS and NO. See also Zakhary, R. et al. (1997) PNAS (USA) 94: 14848.
There is almost universal recognition that NO functions as a neurotransmitter. There is emerging evidence that NO provides functions in the GI tract, particularly the intestine, stomach and pylorus. See e.g, Huang, P. L. et al. (1993) Cell 75: 1273.
In particular, loss of pyloric nNOS has been associated with gastric outflow obstruction. NO has also been implicated in reducing of isolated pyloric pressure waves, altering distribution of liquid glucose within the stomach, slowing gastric emptying, and reducing stomach tone.
There have been problems establishing firm relationship between NO effects and GI function.
For example, there is belief that NO may inhibit gastric emptying in humans, although in some animal models, nNOS is thought to delay that process. In addition, it has been difficult to establish how nNOS expression is regulated, particularly in vivo. These and other drawbacks have impeded efforts to develop therapies that involve increasing or decreasing endogenous NO levels.
There is general understanding that cyclic guanosine monophosphate (cGMP) is an important cell messenger molecule. Enzymes termed phosphodiesterase (PDE) are primarily responsible for destroying cGMP, typically by catalyzing hydrolytic reaction between the cGMP and water. There have been reports of ten (10) PDE families with each have a distinctive tissue, cellular and subcellular distribution. Some PDE families are thought to prefer cyclic adenosine monophosphate (cAMP) as a substrate instead of cGMP.
Numerous PDE inhibitors have been disclosed. For example, PDE type III and IV inhibitors have been reported. See eg., U.S. Pat. Nos. 4,753,945; 4,837,239; 4,971,972; 5,091,431; 6,054,475; 6,127,363; and 6,156,753; as well as referenced cited therein. See also Komas et al. in Phosphodiesterase Inhibitors (1996) (Schudt et al. eds) Academic Press, San Diego, Calif.
Particular attention has focussed on inhibitors of type V PDE, one of the cGMP preferred enzymes. For example, certain of the inhibitors such as sildenafil (Viagra(trademark)) have been reported to treat male erectile dysfunction. See e.g, U.S. Pat. Nos. 6,100,270; 6,207,829 and references cited therein.
There has been much work addressing the biological action of insulin. See generally Kahn, C. R. et al in The Pharmacological Basis of Therapeutics, 8th ed. (Gilman, A. G et al. eds) McGraw-Hill, Inc. New York.
See also U.S. Pat. Nos. 4,916,212; 4,701,440; H245 filed on Jun. 27, 1984; U.S. Pat. Nos. 4,652,547; and 4,652,525 (disclosing a variety of insulin molecules).
It would be useful to have methods for treating gastrointestinal (GI) disorders that involve modulating nitric oxide (NO) signaling. It would be especially desirable to have methods for treating GI disorders that enhance or preferably restore normal NO signaling in the presence of pathological levels of neuronal nitric oxide synthase (nNOS).
The present invention generally includes methods for preventing or treating gastrointestinal (GI) disorders. In one aspect, the invention provides methods for treating the disorders by modulating nitric oxide (NO) signaling pathways particularly in GI neurons. Preferred invention methods involve administering at least one compound that modulates the pathways by increasing one or more of NO activity or levels of neuronal nitric oxide synthase (nNOS). The invention has a wide spectrum of useful applications including treating a variety of gastropathies by administering a therapeutic amount of at least one of insulin or a phosphodiesterase (PDE) inhibitor such as sildenafil (Viagra(trademark)).
We have discovered that by modulating NO signaling pathways in GI neurons it is possible to prevent or treat a wide spectrum of disorders. In particular, it has been found that particular NO signaling pathways are damaged in many mammalian GI disorders. Preferred invention methods generally prevent or treat such disorders by enhancing activity of certain identified molecules in the pathway, typically the NO molecule or the enzyme that facilitates production of that molecule ie., the nNOS enzyme. Preferred invention methods suitably increase and more preferably restore normal neuronal NO signaling, thereby helping to prevent, reduce the severity of, or eliminate symptoms associated with many GI disorders.
More particularly, we have found that many, if not all, GI disorders are associated with abnormal neuronal NO signaling. For example, and as will be discussed below, it is believed that many such disorders involve loss of key NO signaling molecules, particularly nNOS enzyme and the NO molecule. Downstream signaling pathways are thought to suffer from this loss. Without wishing to be bound to theory, that loss of key signaling components is thought to negatively impact a wide variety of cell functions important for normal GI function. That is, the cell functions are removed from significant and normal NO modulation. Loss of that control is believed to facilitate the onset of or aggravate the GI disorders. Increasing or restoring that control is thus a key objective of this invention. Importantly, the invention provides, for the first time, therapeutic methods for preventing or treating the GI disorders by modulating NO signaling pathways. As discussed, preferred invention methods provide at least one of more nNOS enzyme or increasing activity of the NO molecule particularly in GI neurons.
Accordingly, and in one aspect, the invention provides methods for preventing or treating at least one and preferably one gastrointestinal disorder in a mammal suffering from or susceptible to the disorder. In one embodiment, the method includes administering to the mammal a therapeutically effective amount of at least one compound that preferably achieves at least one of:
a) increased nitric oxide (NO) activity e.g. in gastrointestinal neurons or interstitial cells of Cajal as measured in a standard gastric emptying assay (such assay defined herein), or
b) provides for increased nitric oxide synthase (nNOS) levels e.g. in the gastrointestinal neurons or the interstitial cells as measured in a standard nNOS protein expression assay (such assay defined herein).
The foregoing general invention method suitably modulates the NO signaling pathway. More particularly, the method provides, for the first time, a way of therapeutically amplifying this important pathway in the presence of abnormal levels of NO or nNOS enzyme. Thus, the method beneficially provides to xe2x80x9cat riskxe2x80x9d or diseased GI neurons at least one of increased NO activity or increased levels of the nNOS enzyme. This important invention feature desirably increases and preferably restores NO signaling typical of normal GI neurons. Additionally, the methods of the invention may provide supra-physiologic (higher than normal) levels of NO, nNOS, cGMP, etc. which can have important therapeutic benefits, for instance in the treatment of irritable bowel syndrome and other disorders. Without being bound by any theory, by such actions, the GI disorder thus can be prevented or treated by practice of the method.
In some invention embodiments, the recited compound suitably increases both the NO activity and levels of nNOS. However in most embodiments, preferred compounds will increase only one of those characteristics optimally.
In other embodiments, the invention provides for administration of at least two of the compounds discussed above in which a first compound preferably increases the NO activity and a second compound preferably provides for increased levels of the nNOS enzyme. This illustration of the invention is significant because it exemplifies a xe2x80x9ctwo-prongedxe2x80x9d approach to increasing NO signaling therapeutically ie., by boosting NO activity with the first compound and increasing nNOS levels with the second compound. This therapeutic strategy may be indicated in settings in which subjects suffer from or are susceptible to especially hard-to-manage or chronic GI disorders. Administration of the first and second compounds can be conducted as needed e.g., at substantially the same time (co-administration of the first and second compounds) or different times to achieve an intended therapeutic outcome.
Preferred methods in accord with the invention employ mammals, preferably a primate, rabbit, or rodent, more preferably a human subject, which mammal has been identified and selected for therapeutic treatment according to the invention. That is, the mammals have been identified and selected to benefit from an increase in at least one of the NO activity or the nNOS level as discussed above. In this instance, at least one of the compounds is then administered to the mammal that has been identified and selected. In embodiments in which administration of two or more compounds is intended, such administration can be simultaneous or at one or more different times as needed to prevent or treat a specific GI disorder.
In other examples of the invention method, the amount of the administered compound is generally sufficient to increase neuronal cyclic guanosine 3xe2x80x2-monophosphate (cGMP) levels suitably as measured by a standard cGMP assay. As discussed above, cGMP is an important molecule xe2x80x9cdownstreamxe2x80x9d in relation to NO that is believed to assist signal transmission to the cell. By enhancing the cGMP levels, the invention facilitates such transmission particularly under conditions of less than optimal NO molecule or nNOS enzyme levels. The standard cGMP assay is provided in the discussion and examples that follow.
Therapies of the invention are especially effective for the prevention or treatment of a wide spectrum of GI disorders. Preferred GI disorders are those that can be prevented or treated in accord with this invention, preferably by modulating the NO signaling pathways in neurons associated with the GI tract. Additionally preferred disorders include those characterized by hypomotility or hypermotility in at least one of the small intestine, large intestine, colon, esophagus or stomach. Such preferred GI disorders are further characterized by at least one of the following indications: nausea, vomiting, heartburn, postprandial discomfort, diarrhea, constipation, indigestion or related symptoms.
Further preferred GI disorders in accord with the invention are associated with at least one of diabetes, anorexia nervosa, bulimia, achlorhydria, achalasia, anal fissure, irritable bowel syndrome, intestinal pseudoobstruction, scleroderma, or a related disorder. An example of a particular GI disorder is a gastropathy typically associated with diabetes.
Additionally preferred GI disorders suitably prevented or treated by the invention include more particular intestinal pseudoobstruction, preferably at least one of colonic pseudoobstruction (Ogilvie""s syndrome), idopathic gastroparesis,and idiopathic constipation (megacolon).
Still further preferred GI disorders suitably prevents or treated by the invention are those arising from intended or accidental damage to the GI tract eg., stemming from impact or surgical intervention. Other preferred GI disorders in accord with this invention include hypertrophic pyloric stenosis, functional bowel disorder, and gastroesophageal reflux disease (GERD). Preferably, the functional bowel disorder is at least one of irritable bowel syndrome or functional dyspepsia.
The invention also includes methods to treat or prevent (i.e. prophylactic treatment) of Crohn""s disease and ulcerative colitis, comprising administering to a patient suffering or susceptible to such disorders an effective amount of one or more PDE inhibitors and/or insulin or biologically active variant thereof.
Practice of the invention is compatible with a wide spectrum of compounds that have capacity to modulate cell signaling pathways. Examples of such compounds include, but are not limited to, phosphodiesterase (PDE) inhibitors. Particular PDE inhibitors in accord with the invention have been previously reported in U.S. Pat. Nos. 6,100,270; 6,006,735; 6,143,757; 6,143,746; 6,140,329; 6,117,881; 6,043,252; 6,001,847; 5,981,527; and 6,207,829 B1; the disclosures of which patents are incorporated herein by reference.
See also PCT/EP95/04065; WO-A-93/06104; WO-A-93/07149; WO-A-93/12095; WO-A-94/00453; EP 0 463756 B1; and WO-A-94/05661.
See also U.S. Pat. Nos. 4,753,945; 5,010,086; 6,121,279; 6,156,753; 6,054,475; 5,091,431; 6,127,363 and 6,040,309.
See also Komas et al., supra (disclosing additional PDE inhibitors suitable for use with the present invention).
Preferred PDE inhibitors for use with the invention include, but are not limited to, particular bicyclic heterocylic PDE inhibitors, more preferably pyrazolo[4,3-d] prymidin-7-ones, pryazolo[3,4-d] pyrimidin4-ones, quinazolin-4-ones, purin-6-ones, pyrido[3,2-d]pyrimidin-4-ones; as well as pharmaceutically acceptable salts thereof.
A specifically preferred pyrazolo[4,3-d]prymidin-7-one is sildenfil (Viagra(trademark)) also known as 5-[2-ethoxy-5-(4-methylpiperazin-1-ylsulphonyl)phenyl]-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3d]pyrimidin-7-one; as well as pharmaceutically acceptable salts thereof.
Additionally preferred compounds in accord with the invention include insulin or biologically active variants thereof including alleleic varients. A preferred insulin is primate, rabbit, or rodent insulin, more preferably human insulin provided in recombinant form. A wide variety of acceptable insulin molecules have been disclosed. Additional preferred compounds for use in accordance with the invention, particularly in a co-administration regime with a PDE inhibitor is one or more compounds that can boost insulin effects or levels (e.g. by enhancing insulin release, or increasing cell sensitivity to insulin or enhancing insulin""s actions) of a subject upon administration.
Other aspects of the present invention are described below.